1. Field of the Invention
The present invention is concerned with an apparatus for reducing the emission of pollutants in the exhaust gas of an internal combustion engine by modifying the fuel supplied to the engine at least during a start-up period. More specifically, the present invention is concerned with both fractionation and catalytic treatment of conventional liquid hydrocarbon fuel used for an internal combustion engine.
2. Background and Related Art
Apparatuses and techniques for modifying the fuel fed to an internal combustion engine are known in the art. For example, U.S. Pat. No. 3,794,000 to Hodgkinson, dated Feb. 26, 1974 discloses a fuel system for separating volatile fuel from gasoline. The apparatus used in this system comprises a vaporizing chamber into which gasoline is introduced to provide vapors which are removed by a pump and condensed under pressure to form a liquid which is stored in a storage container disposed within the vaporization chamber. The line from the pressurizing pump to the storage container is extended around the storage container to provide additional heat exchange with the gasoline (column 2, lines 54-55 and column 6, lines 30-31) thereby increasing volatilization of the gasoline. When the engine is started the condensate is used as fuel. When the engine reaches a satisfactory operating temperature, a valve cuts off the flow of the condensate and allows normal gasoline to flow to the carburetor (column 5, lines 13-20). The storage container for the condensate includes a level sensor which, when the level of condensate is low, triggers the pump to draw additional vapors from the vaporization chamber. When the vapor pressure in the vaporization chamber is low, additional gasoline is drawn from the gas tank and sprayed into the vaporization chamber (column 5, lines 35-44). In addition, when the storage tank is full, the switch turns the condensing pump off. After the cold-start period, gasoline from both the gas tank and the volatile-depleted gasoline from the vaporization tank are used to run the engine (column 5, line 65 through column 6, line 15).
U.S. Pat. No. 4,394,002 to Allen, dated Sep. 14, 1982, discloses an apparatus and a method for fractionating the gasoline fuel for an internal combustion engine, and combusting the different fractions in repeating sequence in the engine in order to improve fuel mileage. Heat from the engine is utilized via the engine coolant in the fractionation process.
U.S. Pat. No. 3,855,980 to Weisz et al, dated Dec. 24, 1974 discloses a fuel system for an internal combustion engine in which conventional fuel from a fuel tank is passed through a zeolitic catalytic converter heated by engine exhaust gases before being supplied to the engine. The effect of the catalyst is said to improve the octane content of the fuel fed to the engine.
U.S. Pat. No. 4,429,675 to Talbert, dated Feb. 7, 1984 teaches the separation of conventional liquid fuel (gasoline) into a vapor fraction and a liquid fraction using either ultrasonic energy or the heat in the exhaust gases of the engine. The heavier fraction is used, if at all, only at start-up. Other patents teach generally the use of light fractions of a fuel. See, e.g., U.S. Pats. Nos. 1,202,610; 1,384,512; 4,441,477; 3,800,533; 4,562,820; 3,963,013 and German Patent document DE 3002-544, dated Jul. 31, 1981.